Has Halo 3 used its Battle Rifle butt to jack slap Mass Effect sales?

With the big announcement yesterday of Halo 3 being released September 25th, 2007, it got me to wondering how this will affect other games that were already scheduled to be released at that time.
Peering into my video game crystal ball I see some really big titles that could be hurt by this announcement. First and foremost is BioWare’s Mass Effect, but also Assassin’s Creed, TimeShift, and to a lesser extent Grand Theft Auto IV. Lets face it Halo is the game that every developer wishes they had, and no one but no one wants to go against. I am actually looking forward to see what Sony will throw out in the month of September to try to steer some of the PR hype away from the Halo release. Nintendo has a whole string of their heavy hitters coming this fall, but Halo 3 is so big that it could really cut into their sales as far as the Wii60 homes go.
I was really looking forward to Mass Effect, Assassin’s Creed, and Grand Theft Auto IV. I had planned to bang through Mass Effect this summer, in time to work on Assassin’s Creed this September but figured I could have that game finished by the time Grand Theft Auto IV made its way onto consoles in October from there with a few late nights I am guessing I could be very close to finishing GTA IV to finish off 2007 with Halo 3 in November. But with Halo 3 coming in September, and the fact that all the Halo series have always had such strong multiplayer functionality, many gamers could be playing Halo 3 way into 2008, and picking some of these other could have been big titles up later next spring after some price drops. Microsoft may find it more difficult to negotiate deals for exclusive and simultaneous release for cross platform development projects next time due to the fact that developers will worry about AAA first party titles like Gears of War or Crackdown sequels being released in close proximity their games.
Only time will tell how sales will be affected. Lets face it right now all most of us care about is Bungie getting the Halo 3 beta working for us Crackdown owners!